ACPI: add _PDC input override mechanism

In order to have Dom0 call _PDC with input fully representing Xen's
capabilities, and in order to avoid building knowledge of Xen
implementation details into Dom0, this provides a mechanism by which
the Dom0 kernel can, once it filled the _PDC input buffer according to
its own knowledge, present the buffer to Xen to apply overrides for
the parts of the C-, P-, and T-state management that it controls. This
is particularly to address the dependency of Xen using MWAIT to enter
certain C-states on the availability of the break-on-interrupt
extension (which the Dom0 kernel should have no need to know about).

Signed-off-by: Jan Beulich <jbeulich@novell.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/xen/arch/x86/platform_hypercall.c b/xen/arch/x86/platform_hypercall.c
index f6bcb59bec..db5554c47f 100644
--- a/xen/arch/x86/platform_hypercall.c
+++ b/xen/arch/x86/platform_hypercall.c
@@ -415,6 +415,15 @@ ret_t do_platform_op(XEN_GUEST_HANDLE(xen_platform_op_t) u_xenpf_op)
             ret = -EINVAL;
             break;
 
+        case XEN_PM_PDC:
+        {
+            XEN_GUEST_HANDLE(uint32) pdc;
+
+            guest_from_compat_handle(pdc, op->u.set_pminfo.u.pdc);
+            ret = acpi_set_pdc_bits(op->u.set_pminfo.id, pdc);
+        }
+        break;
+
         default:
             ret = -EINVAL;
             break;